The invention relates to a developer apparatus for developing diazotype copy sheets and, more particularly, to the operation and control of metering and pressure blades with which the developer apparatus is equipped for controlling, respectively, the amount of liquid developer applied to the roller's surface and the amount of pressure applied to the copy sheet as it passes through a developing zone between the pressure blade and the applicator roller for development.
Developer apparatuses equipped with metering and pressure blades for developing diazotype copy sheets by applying thereto metered quantities of liquid developer are disclosed, for example, in U.S. Pat. Nos. 3,702,096; 3,704,661; and 3,704,662, assigned to the assignee of the present invention. In these prior art devices, the metering and pressure blades are mounted for pivotal movement into and out of pressure engagement with the applicator roller. Movement of the blades is effected automatically by a cam control means which is fairly complex in construction and expensive to produce. In one of these devices, for example, the device requires mechanism comprising a drive system including two motors and special circuitry for each motor. Moreover, because of the space requirements for such mechanism, the device does not lend itself to the construction of a compact apparatus.
Another device is shown in U.S. Pat. No. 3,969,742 also assigned to the same assignee as the present invention, and comprises a series of gears for moving and controlling the metering and pressure blades. One of the gears is adapted for manual movement to render operative a sequence control gear for pivotally moving the blades into and out of engagement with the applicator roller. Also provided are linkage and latching members, switches and circuitry for maintaining the blades in engagement with the applicator roller and for triggering the motor for driving the applicator roller. Such a device is also complex in construction and expensive to manufacture. Further, the device does not provide for developing quality images on copy media of different materials and weights with only an initial setting of the blades with respect to the applicator roller, and requires independent pressure adjustment of the blades for each different copy media to be developed.